Under MA Gen L ch 140 § 122, one must be licensed to sell a gun in the state of Massachusetts before he/she can do so.
To buy a firearm, one must first apply for and get a Firearms Identification Card. However, under MA Gen L ch 140 § 129B, certain individuals may be hindered from getting a gun (for specific reasons). For instance, persons who have been charged and convicted of a crime that is regarded as a felony, misdemeanor (with over 2 years imprisonment term) or violent crime; persons who are aliens and disregard the law, persons who are no longer citizens of the USA by denunciation, etc, cannot purchase a firearm.
There are no laws in the state of Massachusetts that demand that citizens register their guns.
To do this, one must first apply for and get an LTC ( License to Carry).
To apply for an LTC, persons must be up to 21 years old. The following steps must be followed to successfully apply:
He/she must have concluded a safety training course for firearms, and this course must be one approved by MA Gen L ch. 140 § 131P(a).
He/she must apply to the Local Police Department.
In line with the provisions of MA Gen L ch. 140 § 131(F), any person who intends to carry a weapon in the state despite not living in the state is required to apply for and get a temporary license from a recognized/accredited authority in Massachusetts.